This type of casings is commonly used for the aeration of environments and it is associated, on the inner part, to nets or mosquito nets. Considering the frequent use in multi-storey buildings, such as skyscrapers, these casings are subject to constraining safety requirements. In particular, it is required that the hung sash opens in a controlled manner (i.e. it is not subject to abrupt opening due, for example, to sudden wind blows) and that it has a limited displacement angle away from the fixed frame (so as to not allow people to lean out therefrom). In addition, it is required that, once at maximum opening position, the hung sash is permanently locked, so that it cannot close accidentally (again, for example, due to sudden wind blows).
Some examples of window casings like the one described above are known. International patent publication WO2011/036639 discloses a casing which provides a fixed frame and a hung sash which opens with respect to it. The casing can be opened by means of a handle, whose first rotation determines the unlocking of the hung sash, while a second and subsequent rotation determines the opening displacement thereof. The hung sash is connected to the fixed frame by means of articulation devices which allow for the hung sash to have a roto-translation movement with respect to the fixed frame. Further in detail, the devices allow for a roto-translation along top and lower crosspieces of, respectively, the hung sash and the fixed frame, about a vertical axis so that—in the opening position—the hung sash becomes spaced apart from the fixed frame also at the jamb closest to the articulation devices, towards the outside of the room in which the casing is mounted.
The opening and the locking of the hung sash in open position is assisted by a driving arm connected to the handle by means of a kinematic pair made up of a variable pitch rack and by a relative pinion, also of the variable pitch type. The pinion and rack engagement, not only permits the controlled opening of the hung sash but it also prevents for an accidental movement of the arm when completely open (thus preventing the inadvertent locking of the hung sash).
The casing as described has a complex construction, hence is quite expensive in terms of manufacturing. Besides, the structural complexity makes the casing poorly adaptable to be used with conventional and standard solutions such as for example rotational hinges of the traditional kind. Moreover, the opening system applied to the casing of WO2011/036639 is not adapted to be used on very heavy casings; indeed, the articulation devices used in such casing have a limited load capacity and the number thereof cannot be increased (with the aim of distributing the load) when the weight to be supported increases.
Further examples are known from patents CN101131061 and U.S. Pat. No. 7,464,619. In both documents, devices for the manual opening of a hung sash are described, comprising a manoeuvre lever which uses, for driving the movement of the hung sash, a gear mechanism which prevents the accidental closing of the hung sash from the opening position.
Also document GB2183723 describes an opening system which makes use of a gear mechanism of the pinion/rack type. The latter is connected to a crank handle which, under the manual actuation of a user, drives the gear mechanism for the actuation of a pantograph linkage which opens the window.
Further examples of similar known devices are disclosed by German publications DE1708449 and DE681093.
Generally speaking, all the aforementioned further examples are in turn structurally complex and expensive from a productive point of view. The actuation is troublesome and uncomfortable for the user, in comparison with a conventional window, i.e. a window having a traditional opening using a handle which, besides to being more comfortable to grip and easy to use, it would be more appreciated by the user also from an aesthetical standpoint.